Poison dart frogs have long fascinated researchers. Their toxins are now being linked to the death of Russian opposition leader Alexei Navalny.
A joint report linking poison dart frog toxins to the death of Russian opposition leader Alexei Navalny has quickly caused ripples around the world among scientists.
The allegations raised new questions about the circumstances of Navalny’s death in 2024 and the origin of the highly unusual toxin.
Poison dart frog species have long fascinated researchers and the public because of their small size, striking color patterns, and myths surrounding the deadly venom in their bodies.
But the toxin reportedly identified in the incident, epibatidine, is not known to have been used to kill anyone, Kyle Summers, professor emeritus of biology at East Carolina University, told USA TODAY.
A report released Saturday by Britain, Germany, France, Sweden and the Netherlands said the government was “confident” that Navalny had been poisoned, based on traces of epibatidine found in his system. Navalny, a lawyer, was imprisoned in Siberia at the time of his death. The report noted that the toxin is only found naturally in poison dart frogs in South America, not Russia. Governments have not released toxicology reports and the Russian government has denied the allegations.
Epibatidine has intrigued researchers for decades and was once highly sought after as a potential painkiller many times more powerful than morphine. Summers said it’s possible that a chemical lab thousands of miles away from the rainforest could have artificially recreated the toxin, but many questions remain.
How did we learn about poison dart frog toxins?
John Daly, a biochemist at the National Institutes of Health, pioneered the study of toxin species in poison dart frogs during decades of research, tracing the origin of the poison to the frog’s diet, said Joe Schwartz, director of McGill University’s Department of Science and Society. He traced the origin of the poison to frog food.
Enzymes in the frog’s body convert alkaloids from ants, small beetles, millipedes and mites into toxins, Schwartz said in an article first published in the Montreal Gazette. The Daily has identified epibatidine in poison dart frogs from Ecuador. epididobates tricolor.
Initially, researchers had high hopes for this poison. Although highly toxic, researchers have found that it has an analgesic effect that is 200 times more powerful than morphine and may not be associated with addiction.
The idea that epibatidine “could be a potentially useful pharmacological tool as an analgesic” stimulated a great deal of interest and motivation, Summers said. “Ultimately, if we can make it function as an analgesic, there could be incredible benefits.”
Scientists were able to decipher the toxin and recreate it chemically, but the gap between beneficial and lethal doses proved too narrow to be viable.
Is the epibatidine reportedly found in Navalny’s body man-made?
Some indigenous tribes in the rainforest were known to use the poison dart frog batrachotoxin for hunting, but scientists have found no evidence that epibatidine was used for that purpose.
Summers noted that while the governments’ statements did not specify Navalny’s cause of death, it would be noteworthy if the governments were able to identify epibatidine in samples from his body.
Summers said it would be “very surprising” if someone tried to use the product as an experimental chemical to poison someone.
The UK and other governments said in a statement that they had notified the Organization for the Prohibition of Chemical Weapons of findings that may indicate a violation of the Biological and Toxin Weapons Convention. He also said the findings raise concerns that Russia may not have destroyed all of its chemical weapons.
What you need to know about poison dart frogs
Frogs that live in South America’s rainforests face risks from habitat destruction and the exotic pet trade. More than 175 species have been confirmed. Researchers found that captive poison dart frogs are generally not poisonous because they are not fed the same diet as wild frogs.
Summers said the frog’s colorful markings warn predators of danger. They advertise the toxin and predators know to avoid it, he added. Frogs have evolved to be resistant to toxins.
Summers, one of several scientists who has studied poison dart frog coloration over the years, said the bright colors can be imitated by non-venomous frogs to trick predators into believing they are dangerous, or by other venomous frogs to join forces to warn predators away.
Yusang Yang, an assistant professor at the University of South Florida, told USA TODAY that colors are also used in mate selection and competition.
Females usually prefer males that are the same color or brightly colored. And males become more aggressive when their mate is bright and of the same color.
Summers said many poison dart frog species differ from other frogs in that they abandon their eggs and hatch on their own. He and Yang explained how the adults worked together to transport the tadpoles to a small pool.
“The tadpoles wriggle on the male’s back, and the male goes into a small pool,” Summers said. “Over a period of several months, they will be visiting the pool again.”
Scientists say females lay eggs for the tadpoles to eat and survive. Such monogamous pairings are “very rare for frogs,” Summers said.
The mating behavior is likely acquired when the tadpoles memorize their mother’s colors while feeding, and as they grow older they begin to show a bias toward the remembered colors, Yang said.
Dinah Boyles Pulver, a national correspondent for USA TODAY, covers climate change, wildlife and the environment. Contact dpulver@usatoday.com or @dinahvp on Bluesky or dinahvp.77 on X or Signal.
